Operation of a tire vulcanization system

ABSTRACT

In an electric vulcanization process, open loop and closed loop control modes can be used for controlling a heater output.

TECHNICAL FIELD

The presently disclosed invention is generally directed to tirevulcanization. More particularly, the presently disclosed invention isdirected to determination of the energy balance in a tire vulcanizationsystem.

BACKGROUND

During vulcanization of a tire, one or more tire vulcanizing systems maybe employed for use with a tire mold. A principal characteristic ofcertain vulcanization systems is to place a system of heating andventilation at the heart of an electric vulcanization system and thusprovide a heated medium. For example, in an electric press, after agreen tire is charged in a mold, supply of a high-temperature andhigh-pressure heating medium (hereinafter “heating medium”) into abladder (i.e., one formed from an elastic material such as butyl rubber)causes the bladder to expand and thereby engage an inner wall surface ofthe tire.

Referring to FIG. 1, an exemplary tire vulcanizing system 10 of thistype is shown for vulcanizing a green tire P. System 10 includes afluid-tight enclosure 12 that receives a supply of a pressurized heatingmedium (e.g., nitrogen gas). The enclosure has a cavity 14 formed by apair of plates 16, 18 connected by a bladder 20 with an operating shaft22 effecting axial movement of at least one plate (as shown, plate 16 isaxially displaceable). A heater 24 having one or more heating elements24 a heats the heating medium. It is understood that heater 24 may beselected from any amenable heating means, including but not limited toresistors, induction elements and the like. A fan 26, driven by anensemble of a rotor 30 and a stator 31 (together forming a motor),agitates the heating medium at a high speed ω with respect to heater 24so that heat is supplied to the heating medium at a high heat exchangeratio. Both heater 24 and fan 26 are enveloped within cavity 14 andtherefore immersed wholly in the heating medium.

Heater 24 is disposed in a fluid path that is in communication with bothcavity 14 and at least one conduit 32 through which the heating mediumis introduced into, and/or extracted from, cavity 14. The heating mediumtraverses heating elements 24 a before egress along an exit path 26 afrom fan 26 into the fluid-tight enclosure. The delivery of the heatingmedium provides sufficient energy to bladder 20 for deep penetration oftread pattern elements of the tire mold (not shown) into tire P. Tire Pis thereby heated to a vulcanizing temperature through bladder 20 andsimultaneously pressed in a molding direction. Exemplary embodiments ofsuch systems and demonstrations of their use are disclosed by co-ownedEP Patent No. EP 0686492 for TYRE VULCANISATION BY SUPPLYING HEAT FROMTHE INSIDE, filed 18 May 1995, and co-owned and co-pending PCTPublication No. WO2013/164282 for a CHAMBER FOR VULCANIZING THE INNERPORTION OF A TIRE AND INCLUDING A FAN, filed 26 Apr. 2013, the entiredisclosures of which are incorporated by reference herein.

As further illustrated in FIG. 2, the heating medium is subject torotation under the effect of relative movement imparted by fan 26. Theheating fluid attains sufficient tangential speed Ω within the cavity soas to ensure a good thermal exchange with the internal surface ofbladder 20. In order to ensure this advantageous thermal exchange, theheating medium exhibits a speed Ω (see FIG. 1) that derives thenecessary vulcanization energy from heater 24 and delivers it to aninternal surface of bladder 20.

As pressure changes during a cure cycle, it is contemplated thathomogenization of the temperature through the entire volume of theenclosure can be effected. To determine and monitor thermal transferbetween the heating medium and the molded tire across the bladder, fluidtemperature would be ideally determined along an internal surface of thetire. While some vulcanization processes contemplate the capture of thetemperature of a heating medium, sensors for such purposes are usuallyarranged exterior to the fluid-tight enclosure (e.g., being arranged inpipelines or supply lines for the heating medium).

Measuring fluid temperature along internal tire surfaces presents acomplex and expensive challenge. Therefore, reliable and predictabledetection and monitoring of the heating medium is demanded for theduration of time under which the heating medium remains under pressure.Such detecting and monitoring, effected within the fluid-tightenclosure, can translate into control of heat transmission to the tirethrough the heating medium and bladder.

SUMMARY

The invention provides a method of operating a tire vulcanization system(100) during a curing cycle in which a tire (P′) is vulcanized in a moldfor a predetermined duration under pressure. The tire vulcanizationsystem (100) includes a bladder (120) disposed inside a tire to bevulcanized and at least partially delineating a cavity (114) in which aheating medium circulates. A fan (126) and a heater (124) are immersedin the heating medium, and the heater has one or more heating elements(124 a) that provide energy to the heating medium traversing thereover.The method includes providing data that includes at least a bladderexchange surface area (S) for a tire being vulcanized, a temperaturedifferential (ΔT) between the bladder and the heating medium and acoefficient of exchange by forced convection (h). A heating mediumtemperature in the cavity is detected during a current curing cycle. Theheating medium temperature in the cavity (114) is adjusted by adjustingthe power output of the heater (124).

In some embodiments, the method includes configuring at least onetemperature sensor (150) that is disposed along an exit path (126 a)from the fan into the cavity to perform the detecting and to generateone or more temperature signals indicative of the detected heatingmedium temperature. A monitoring system may be configured to receive thetemperature signals and to send one or more commensurate control signalsto perform the adjusting.

In some embodiments, the method also includes at least one of initiatinga timer upon introducing the heating medium into the cavity formonitoring an elapsed time of the duration under pressure; on the basisof the detected heating medium temperature, calculating a thermal flux(ϕ) that traverses the bladder during a subsequent curing cycle as afunction of at least the bladder exchange surface area (S) and thetemperature differential (ΔT) between the bladder and the heatingmedium; comparing a calculation of the thermal flux (ϕ) with a requiredthermal flux to be realized upon commencement of the subsequent curecycle; and performing the adjusting when a comparison indicatesnon-equivalence.

The adjusting can include attaining a predicted final heating mediumtemperature upon termination of the current curing cycle. The adjustingcan also include at least one of adjusting a fan speed, adjusting aheating medium pressure and adjusting a heater output, and whereinadjusting the heater output by adjusting a heater supply voltage. Theadjusting can further include increasing the heater output during aphase of the elapsed time necessary to attain and maintain apredetermined temperature level of the heating medium, during apredetermined time less than or equal to the duration under pressure.

The invention also provides a method of operating a tire vulcanizationsystem (100) that includes providing data that includes at least abladder exchange surface area (S) for a tire being vulcanized, atemperature differential (ΔT) between the bladder and the heatingmedium, and a coefficient of exchange by forced convection (h). Aheating medium temperature in the cavity is detected during a currentcuring cycle. Based upon an energy balance to define the amount ofenergy to be sent by the vulcanization system (100) in advance of asubsequent curing cycle, a heating medium temperature in the cavity(114) is detected during a current curing cycle. Based upon a detectedheating medium temperature, the energy to be sent by the vulcanizationsystem (100) in advance of the subsequent curing cycle is adjusted.

In some embodiments, this method includes calculating an energy requiredto cure the tire being vulcanized as a function of at least the energyto be supplied for vulcanization of an inner tire surface, energy lostupon opening the mold between the current curing cycle and thesubsequent curing cycle and energy lost by the vulcanization systemduring curing.

The invention also includes a tire vulcanization system (100) forperforming the disclosed methods.

Other aspects of the presently disclosed invention will become readilyapparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The nature and various advantages of the presently disclosed inventionwill become more apparent upon consideration of the following detaileddescription, taken in conjunction with the accompanying drawings, inwhich like reference characters refer to like parts throughout, and inwhich:

FIG. 1 shows an exemplary conventional electric vulcanization system.

FIG. 2 shows a simulation of a circulation of flux in the conventionalvulcanization system of FIG. 1.

FIG. 3 shows a partial sectional view of an exemplary vulcanizationsystem.

FIG. 4 shows a sectional view of the exemplary vulcanization system ofFIG. 3 upon collapse of a curing bladder.

FIG. 5 shows an exemplary closed-loop embodiment of a process forcontrolling a heating medium temperature.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments of the invention,one or more examples of which are illustrated in the drawings. Eachexample is provided by way of explanation and not by limitation of thepresently disclosed invention. It will be apparent to those skilled inthe art that various modifications and variations can be made in thepresent invention without departing from the scope or spirit of theinvention. For instance, features illustrated or described as part ofone embodiment can be used with one or more other embodiments to yieldat least one further embodiment. Thus, it is intended that the presentinvention covers such modifications and variations as come within thescope of the appended claims and their equivalents.

Now referring further to the figures, in which like numbers identifylike elements, FIGS. 3 and 4 show an exemplary tire vulcanization system100 having many of the characteristics of system 10 shown in FIG. 1.Vulcanization system 100 includes an axially movable plate 116 and astationary plate 118 connected by a flexible bladder or curing membrane120. Counterplates 117, 119 anchor bladder 120 to respective plates 116,118 along a circumference thereof. Bladder 120 and plates 116, 118together delineate a fluid-tight enclosure 112 having a cavity 114 forcontaining a heating medium under pressure (e.g., nitrogen). Bladder 120cooperates in a known manner with a rigid tire mold (not shown) intendedto form an outer tire shape and sculpture.

A heater 124 is enveloped within cavity 114 and therefore immersedwholly in the heating medium during operation of system 100. Heater 124is shown as a coil member having heating elements 124 a generally formedin an annular shape, although it is understood that heater 124 may beselected from known heater mechanisms that are amenable to practice withthe presently disclosed invention. Annular heating elements 124 a areamenable to operation with a fan 126 having a plurality of blades 126 band a diametrical extent 126 c. One or more blades 126 b may have a highthermal conductive material at least partially integrated therewith,including but not limited to copper, aluminum and comparable andequivalent materials. A power source (such as an electric power source,not shown) that is in communication with heater 124 and fan 126 ensuresuninterrupted control and operation of both elements within cavity 114.

A central portion of enclosure 112 includes an operating shaft 122 thatis rotatable relative to fixed mold 123 along an axis of revolution X-X′of the enclosure. Operating shaft 122 effects exemplary axial movementof plate 116 between a vulcanization position in which bladder 120 abutsan inner wall surface P_(s)′ of tire P′ (see FIG. 3) and an extractionposition in which bladder 120 collapses (see FIG. 4). Rotor 130 effectscircumferential rotation of a substrate 125 supporting fan 126. As isknown in the art, rotor 130 sufficiently actuates fan blades 126 b so asto impart a proscribed tangential velocity to the ejected heatingmedium.

Upon commencement of a curing cycle in which a tire (P′) is vulcanizedin a mold for a predetermined duration under pressure (herein “durationunder pressure”), one or more conduits 132 that are delineated in astationary housing body 134 introduce pressurized heating medium intocavity 114. The heating medium is introduced into the cavity as needed(e.g., continuously or periodically) to maintain sufficient heattransfer along bladder 120 and wall 120 a thereof. A valve (not shown)may be provided for automatic introduction and extraction of the heatingmedium. The heating medium is supplied from a heating medium supply (notshown) as is known in the art. Such heating medium supply may optionallyinclude a preheating device that previously heats the heating mediumprior to introduction thereof in cavity 114. It is understood thatconduit 132 may include one or more conduits that are also employed forthe extraction of the heating medium upon termination of a curing cycle.

The heating medium may be selected from a plurality of heating mediaamenable to use with a vulcanization system as presently described. Insome embodiments, the heating medium is nitrogen which exhibitsnegligible interdependence between pressure and temperature. When theheating medium is nitrogen (or an equivalent thereof), independentcontrol of the temperature of the heating medium is possible.

Upon actuation of fan 126, the heating medium is drawn through a centralportion thereof, traverses heating elements 124 a and is ejected alongexit path 126 a into cavity 114. At least one heating medium temperaturesensor 150 (e.g., a thermocouple or equivalent thereof) is disposedintermediate housing body 134 and diametrical extent 126 c. In someembodiments, temperature sensor 150 is mounted on stationary plate 118immediately proximate an egress from which fan 126 delivers the heatingmedium to exit path 126 a. Temperature sensor 150 is configured todetect a temperature of the heating medium in cavity 114 and generatesone or more temperature signals indicative of the detected temperature.It is contemplated that temperature sensor 150 may capture the heatingmedium temperature continuously (e.g., at each instant while a greentire is subject to the pressurized heating medium) or at regularpredetermined time intervals.

During a present cure cycle as shown in FIG. 3, bladder 120, under theeffect of the pressure of the heating medium, is in a deployed positionpressed along inner wall surface P_(s)′ of tire P′. Upon extraction ofthe heating medium from cavity 114 as shown in FIG. 4, axial movement ofplate 116 is effected within pre-defined limits (e.g., in the directionindicated by arrow A) such that bladder 120 collapses toward the centralportion of fan 126 (e.g., in order to free space for the passage of abead). Collapse of bladder 120 positions the bladder in a ready statefor a subsequent cure cycle without contacting blades 126 b ortemperature sensor 150. The positioning of temperature sensor 150therefore not only ensures effective temperature data capture throughouta curing cycle; it also protects the sensor from damage duringextraction and preserves uninterrupted operability of the sensor formultiple curing cycles.

Temperature sensor 150 may be coupled to a monitoring system (not shown)that is configured to receive the temperature signals generated thereby.The monitoring system generates one or more control signals in responseto the temperatures detected by temperature sensor 150. Such controlsignals are used to command the heater.

Internal Control of an Electric Vulcanization System

The monitoring system thus receives the temperature data signals andsends a commensurate heating instruction to heater 124 on the basis ofthe received temperature data, the desired temperature of the heatingmedium, the heating time of the heating medium and other factors. Withinan electric vulcanization system, such factors are typically set up by apre-established cycle that has been obtained from observed experimentaldata. In the art, it is generally understood that agreement betweentheory and experiment is very good. The applicable temperature, pressureand mold residence time can be thus regulated (e.g., via on-linecontrol) to enable different elastomer compositions to attains a desiredcrosslinking degree.

The rotational speed of fan 126 must be sufficiently high so that heattransfer toward the tire is assured. Simultaneously, temperature sensor150 (as shown and described with respect to FIGS. 3 and 4) captures thetemperature of the heating medium supplied to cavity 114, thereforeproviding a pertinent representation of the temperature of the heatingmedium along inner wall surface 120 a of bladder 120.

To counteract the thermal resistance of the bladder, heat flux may becontrollably increased during a current curing cycle to ensuresufficient heat flux for vulcanization upon commencement of a subsequentcuring cycle. The sensed heating medium temperature may therefore berelied upon in one or more processes for optimizing the transmission ofenergy by controlling the combination of heater 124 and fan 126.

Assuming that bladder 120 represents the greatest thermal resistanceacross which energy must be transmitted to the tire, the thermal fluxthat traverses the bladder may be expressed as:Φ=h×S×ΔT  (EQ. 1)wherein:

Φ is the thermal flux (heat transferred per unit time) in W;

h is the convection heat transfer coefficient in W/(m²° C.), which islinked to the speed of the heating medium relative to the interior wallof the bladder, and with the speed of the heating medium being linked tothe rotational speed of the fan;

S is the area of the exchange surface (i.e., the heat transfer area ofthe bladder surface) in m², which is linked to a geometry of the mold inwhich the tire is formed; and

ΔT is a temperature difference between the heating medium and themembrane surface in ° C.

Thus, by providing data that includes at least a bladder exchangesurface area (S) unique to each tire being vulcanized, a temperaturedifferential (ΔT) between the bladder and the heating medium unique toeach tire being vulcanized, and a coefficient of exchange by forcedconvection (h) unique to each established cure cycle.

Opened loop and closed loop control modes can be used for controllingheater 124. An opened loop control mode is based upon energy control. Inthis mode, it necessary to realize an energy balance of vulcanizationsystem 100 and thereby define the amount of energy to send to heater 124prior to curing. This amount of energy is computed according to thephysical characteristics of the green tire, the energy losses realizedduring curing and the energy losses realized during press opening. Someadjustments can be done during the curing, including a power adjustmentaccording to the opening duration of the press and an additionaladjustment according to the heating medium temperature that is measuredduring a previous curing.

To realize open-loop control of the internal portion of system 100, itis necessary to determine the total required energy to be delivered byheater 124. This energy will raise the temperature of the heating mediumand thereby control the rate of heat transfer across the curingmembrane. The total energy to be supplied by the heater is obtainablefrom the energy to be supplied for the vulcanization of the interior ofthe tire; the energy lost by convection during opening of the tire mold;the energy lost by all mechanical parts of the vulcanization system 100during curing; and the energy supplied by rotor 130 (e.g., the energyneeded to propel fan 126). In order to observe the temperature of theheating medium, temperature sensor 150 may be employed.

The energy that is needed for vulcanization of a tire is the energy thatcarries the tire from its initial temperature (e.g., ambienttemperature) to its desired vulcanization temperature (e.g., as definedby applicable curing laws). This energy is supplied internally by theheating medium and externally by the mold. Based upon experience withmultiple curing presses and confirmed by tests carried out on electricalpresses, it is observed that the external energy contribution comprisesup to about two-thirds of this energy and the internal contributioncomprises up to about one-third.

At each instant of the duration of the opening of the mold, the thermalflux (in W) observed at movable plate 116 and bladder 120 can becalculated in order to determine the energy lost during opening of thetire mold. System 100 includes axially movable plate 116 in contact withambient air and stationary plate 118 having no contact with ambient air.

In order to determine energy that is lost via the mechanical parts ofthe thermal system 100, the thermal flux (in W) realized at the housingbody can be calculated at each instant of the duration under pressure.The thermal flux is deemed constant along stationary plate 118, whilethe thermal flux realized at housing body 134 decreases at the same rateas the temperature thereof. The thermal flux that exits the mechanicalparts of the vulcanization system 100 for the duration under pressuremay thus be expressed in terms of initial and ambient temperaturesaround the housing body.

Based upon experience with multiple curing presses and confirmed bytests carried out on systems commensurate with system 100, the powerthat is consumed by rotor 130 remains essentially constant in that it isnot dependent on the size and shape of a tire's internal cavity. Theenergy supplied by rotor 130 can be readily determined as a relationshipbetween the consumed power and the length of the duration underpressure.

The pendency of the duration under pressure may be observed at distinctstages during each of which the total energy to be supplied by theheater may be calculated and adjusted. In an exemplary programmable openloop process, activation and control of heater 124 may be realized in aphase during which the energy is transferred toward the tire uponcommencement of the duration under pressure. With an open-loop control,stability of the heating medium temperature is ensured by capturing suchtemperature during the duration under pressure. In the presentlydisclosed open-loop process, it is observed that a rise in the heatingmedium temperature has a duration that is measured from an initial time.Upon commencement of the duration under pressure, the heating mediumtemperature falls quickly and settles at a limit within a predictabletemperature limit. Thus, power loss can be predicted and the heateroutput adjusted accordingly by adjusting the heater supply voltage.

An optional correction or adjustment may be calculated in which thecoefficient of exchange by forced convection h is presumed to be, onaverage, twice as low at a predicted elapsed time of the duration underpressure as compared with a remainder of the duration under pressure. Tooffset the decline of the exchange coefficient h, the presentlydisclosed method, during a phase of the elapsed time that is necessaryfor the introduction of power that is twice as large as that introducedduring the subsequent remainder of the duration under pressure. Thus,the durations of elapsed time can be adjusted to ensure that the powerrealized does not surpass a maximum power of the heater. For example, inpractice, a limit of 0.90 can be established so as to ensure a powerreserve.

Activation of heater 124 ceases and the system is permitted tohomogenize until the end of the duration under pressure, at which timethe heating medium settles in a final temperature range. The diminutionof the heating medium temperature is linked to the transfer of energytoward the tire and to energy losses from the system. For example, upondeactivation of the heater, the pressure of the heating medium inbladder 120 may be low, thereby resulting in correspondingly low heatexchange. An error calculation may be performed in an experimental modelor simulation such that the power levels are adjusted to compensate forthis captured temperature value.

Likewise, the time during which the mold is open has an effect on thepredicted energy and therefore a commensurate effect on power.Automation of vulcanization system 100 captures a mold open period andtherefore readily calculates an adjustment to power according to thepresently disclosed process.

The presently disclosed process enables reliable and repeatable powerpredictions and thereby permits management of cure while thevulcanization system is in a stabilized state (i.e., the predictedenergy ensures cure of the tire and equally compensates for energylosses). It is understood that different phases of controlling a heaterthroughout a duration under pressure can be effected for any tire sizeand type, as would be understood by a skilled person.

In a closed loop control mode, the objective is to induce the requisitetemperature at the inner wall 120 a of the bladder 120. Temperaturesensor 150 is used to measure and control the temperature at the innerwall 120 a of the bladder 120.

The block diagram of FIG. 5 represents an exemplary programmable controlloop. The setpoint temperature Tc level and duration are defined byexperiment. This duration can be inferior or equal to the duration underpressure. This control may be realized by an exemplary control loop asshown and attained, for example, by a programmable logic controller(PLC). It is understood that a setpoint temperature T_(c) can beestablished for any tire size and type in accordance with applicablecure law, as would be understood by a skilled person.

In the exemplary closed-loop process, heater 124 may be deactivated uponlapse of the duration under pressure so as to ensure homogenizationwithin cavity 114. Homogenization is maintained until expiration of theduration under pressure, at which time the heating medium attains afinal temperature. The decrease in the temperature of the heating mediumis attributable not only to heat transfer to the tire but also to theinherent losses of the vulcanization system.

In embodiments that utilize a closed-loop control, fan 126 may beactivated as soon as the tire is charged in a press and the pressure inthe curing membrane passes a minimum threshold. In such embodiments,operation of fan 126 may be selectively terminated during the entireduration under pressure upon realizing sufficient heat transfer towardthe tire.

In order to verify quality and repeatability of tire curing cycles, averification system is put in place on the vulcanization system. Theprinciple of verification of the extent of cure is based upon theprinciple set out in Table 1 below:

TABLE 1 Type de Verification of the Verification of ComplementaryControl solicitation thermal transfer Verification Closed-loopTemperature Pressure Temperature of the Fan speed heating medium Openloop Output power of the Pressure Temperature of the heater Fan speedheating medium

It is demonstrated that the presently disclosed embodiments allowunimpeded flow of the heating medium while controlling the temperaturethereof throughout a cure cycle and during phases thereof. As taughtherein, an adaptation to shorter curing cycles may be effected withcommensurately truncated pressurization periods. The presently disclosedsystem and method establish a temperature throughout the fluid-tightenclosure that remains homogeneous throughout the cure. This isperformed within generally known vulcanization systems by establishingand maintaining control of the heater without effecting fundamentalchanges to existing procedure.

At least some of the various techniques described herein may beimplemented in connection with hardware or software or, whereappropriate, with a combination of both. For example, electrical dataprocessing functionality may be used to implement any aspect of powercomputation and adjustment, including implementation in connection witha computing device (including a mobile networking apparatus) thatincludes hardware, software, or, where appropriate, a combination ofboth. The processing functionality may correspond to any type ofcomputing device that includes one or more processing devices. Thecomputing device can include any type of computer, computer system orother programmable electronic device, including a client computer, aserver computer, a portable computer (including a laptop and a tablet),a handheld computer, a mobile phone (including a smart phone), a gamingdevice, an embedded controller, a near-field communication device, adevice with applications implemented at least partly using a cloudservice, and any combination and/or equivalent thereof (includingtouchless devices). Moreover, the computing device may be implementedusing one or more networked computers, e.g., in a cluster or otherdistributed computing system. The network may be a LAN, a WAN, a SAN, awireless network, a cellular network, radio links, optical links and/orthe Internet, although the network is not limited to these networkselections. A server may be further configured to facilitatecommunication between at least one module as presently disclosed and oneor more of the computing devices.

Selected combinations of aspects of the disclosed technology correspondto a plurality of different embodiments of the present invention. Itshould be noted that each of the exemplary embodiments presented anddiscussed herein should not insinuate limitations of the present subjectmatter. Features or steps illustrated or described as part of oneembodiment may be used in combination with aspects of another embodimentto yield yet further embodiments. Additionally, certain features may beinterchanged with similar devices or features not expressly mentionedwhich perform the same or similar function.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm.” Also, the dimensions and values disclosed herein are notlimited to a specified unit of measurement. For example, dimensionsexpressed in English units are understood to include equivalentdimensions in metric and other units (e.g., a dimension disclosed as “1inch” is intended to mean an equivalent dimension of “2.5 cm”).

As used herein, the term “method” or “process” refers to one or moresteps that may be performed in other ordering than shown withoutdeparting from the scope of the presently disclosed invention. As usedherein, the term “method” or “process” may include one or more stepsperformed at least by one electronic or computer-based apparatus. Anysequence of steps is exemplary and is not intended to limit methodsdescribed herein to any particular sequence, nor is it intended topreclude adding steps, omitting steps, repeating steps, or performingsteps simultaneously. As used herein, the term “method” or “process” mayinclude one or more steps performed at least by one electronic orcomputer-based apparatus having a processor for executing instructionsthat carry out the steps.

The terms “a,” “an,” and the singular forms of words shall be taken toinclude the plural form of the same words, such that the terms mean thatone or more of something is provided. The terms “at least one” and “oneor more” are used interchangeably. Ranges that are described as being“between a and b” are inclusive of the values for “a” and “b.”

Every document cited herein, including any cross-referenced or relatedpatent or application is hereby incorporated herein by reference in itsentirety unless expressly excluded or otherwise limited. The citation ofany document is not an admission that it is prior art with respect toany invention disclosed or claimed herein or that it alone, or in anycombination with any other reference or references, teaches, suggests ordiscloses any such invention. Further, to the extent that any meaning ordefinition of a term in this document conflicts with any meaning ordefinition of the same term in a document incorporated by reference, themeaning or definition assigned to that term in this document shallgovern.

While particular embodiments of the disclosed apparatus have beenillustrated and described, it will be understood that various changes,additions and modifications can be made without departing from thespirit and scope of the present disclosure. Accordingly, no limitationshould be imposed on the scope of the presently disclosed invention,except as set forth in the accompanying claims.

What is claimed is:
 1. A method of operating a tire vulcanization systemduring a curing cycle in which a tire is vulcanized in a mold for apredetermined duration under pressure, the tire vulcanization systemincluding an axially movable plate and a stationary plate connected by abladder disposed inside a tire to be vulcanized and at least partiallydelineating a cavity in which a heating medium circulates, with a fanand a heater being immersed in the heating medium and the heater havingone or more heating elements that provide energy to the heating mediumtraversing thereover, the method comprising: providing data, for acurrent curing cycle, that includes at least a bladder exchange surfacearea S for a tire being vulcanized, a temperature differential ΔTbetween the bladder and the heating medium, and a coefficient ofexchange by forced convection h; detecting a heating medium temperaturein the cavity during the current curing cycle; on the basis of thedetected heating medium temperature, calculating a thermal flux ϕ thattraverses the bladder during a subsequent curing cycle as a function ofat least the bladder exchange surface area S and the temperaturedifferential; comparing the calculated thermal flux with a requiredthermal flux to be realized upon commencement of the subsequent curingcycle; and adjusting the heating medium temperature in the cavity when acomparison between the calculated thermal flux and the required thermalflux indicates a non-equivalence therebetween.
 2. The method of claim 1,further comprising: configuring at least one temperature sensor toperform the detecting step and to generate one or more temperaturesignals indicative of the detected heating medium temperature, the atleast one temperature sensor being mounted on or near the stationaryplate immediately proximate an egress from which the fan delivers theheating medium and that is disposed along an exit path from the fan intothe cavity; and configuring a monitoring system to receive the one ormore temperature signals and send one or more control signals to performthe adjusting.
 3. The method of claim 1, further comprising: initiatinga timer upon introducing the heating medium into the cavity formonitoring an elapsed time of the duration under pressure.
 4. The methodof claim 3, wherein the adjusting includes attaining a predicted finalheating medium temperature upon termination of the current curing cycle.5. The method of claim 3, wherein the adjusting includes at least one ofadjusting a fan speed, adjusting a heating medium pressure and adjustinga heater output, and wherein adjusting the heater output is accomplishedby adjusting a heater supply voltage.
 6. The method of claim 5, whereinthe adjusting includes increasing the heater output during a phase ofthe elapsed time necessary to attain and maintain a predeterminedtemperature level of the heating medium, during a predetermined timeless than or equal to the duration under pressure.
 7. The method ofclaim 1, further comprising, based on the detected heating mediumtemperature, calculating an energy required to cure the tire beingvulcanized as a function of at least the energy to be supplied forvulcanization of an inner tire surface, energy lost upon opening themold between the current curing cycle and the subsequent curing cycle,and energy lost by the vulcanization system during curing.
 8. The methodof claim 7, wherein the calculated energy is delivered upon commencementof the duration under pressure.
 9. The method of claim 8, wherein,during at least a portion of the duration under pressure, a heatingmedium pressure increases and wherein, during another portion of theelapsed time, the heating medium pressure remains constant.
 10. Themethod of claim 9, wherein the adjusting includes terminating theadjusting so as to attain a predicted final heating medium temperatureupon lapse of the duration under pressure.
 11. The method of claim 7,further comprising, on the basis of predicted energy, calculating anadjustment as a function of the energy lost by the vulcanization systemand a period during which the mold is open.
 12. The method of claim 1,wherein the heating medium comprises nitrogen.
 13. The method of claim1, further comprising providing at least one programmable controller insignal communication with the vulcanization system for programming atleast one of the current curing cycle and the subsequent curing cycle.